1 NOTE: An error in the 1960 rural population count was discovered after the publication of CPH-2-1 from the 1990 Census. 2  The correct 1960 rural population using the 'Current urban definition' is 54,054,425.
Tyr (-5). Phe (-5). Role in structure: Glycine is a very unique amino acid in that in contains a hydrogen as its side chain (rather than a carbon as is the case in all other amino acids). This means that there is much more conformational flexibility in glycine.
R-group Hydrocarbon Neutral Acid or base where the COOH is understood to be the carboxyl group shown above. There are 20 amino acids which make up the proteins, distinguished by the R-group. The simplest of the amino acids, glycine, has just H as an R-group. Amino acids are the structural elements from which proteins are built. When amino acids bond to each other, it is done in the form of an amide, making a connection which is called a peptide linkage. This can be illustrated with the two simplest amino acids, glycine and alanine.